JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdn.rawgit.com/robbmj/simple-js-countdown-timer/master/countdowntimer.js"></script>
<body>
    <a id="startTimer">Start Count Down</a>
    <div>Registration schliesst in <span id="displayTimer"></span> minutes!</div>
</body>

JavaScript

window.onload = function() {
  var display = document.querySelector('#displayTimer'),
    timer = new CountDownTimer(5),
    timeObj = CountDownTimer.parse(5);

  format(timeObj.minutes, timeObj.seconds);

  timer.onTick(format);

  document.querySelector('#startTimer').addEventListener('click', function() {
    timer.start();
  });

  function format(minutes, seconds) {
    minutes = minutes < 10 ? "0" + minutes : minutes;
    seconds = seconds < 10 ? "0" + seconds : seconds;
    display.textContent = minutes + ':' + seconds;
  }
};